The present invention relates to a device for adjusting and varying the bearing position of the plug (mobile part) on the seat (fixed part) of a rotary shaft valve when the valve is closed.
1. Field of the Invention
Almost all single, double or triple offset rotary shaft valves have sealing and adjustment characteristics which are mechanically dependent on the relative position of the plug and the seat on which it bears when the valve is closed.
Sealing and adjustment performance will be optimal only if the theoretical bearing line of the plug of the valve, whether it be circular, elliptical or any other shape, is strictly superposed on and coincident with the same theoretical bearing line of the seat, to achieve this the two bearing lines must imperatively and simultaneously be geometrically identical and superposable in space.
2. Description of Prior Art
In conventional prior art rotary valves with concentric bore bushings it is practically impossible to superpose the bearing line of the plug with the bearing line of the seat; any approximation is realizable in practice only by extremely precise machining of the component parts, leading to a very high manufacturing cost of the finished product; moreover, progressive wear of the component parts modifies the original dimensions of the parts and therefore destroys the original superposition of the bearing line of the plug on its seat and therefore contributes to progressive deterioration of the sealing characteristics, without any possibility of correcting them other than replacing the worn parts with new parts.
The conventional prior art valves cannot correct the reversing of the clearances between the component parts if the direction of the fluid in the valve is reversed.
The device of the invention remedies these drawbacks.
In accordance with the first feature of the invention it has two offset bushings:
By offset bushings we mean bushings whose internal bore is offset relative to the outside surface, the thickness ep (FIG. 3.b) of these bushings in the device of this invention becomes adjustable, so that merely rotating the bushings enables adjustment for correcting, without additional cost:
dimensional variations due to manufacturing tolerances of the component parts (plus or minus relative to the nominal dimension),
wear of the parts,
reversing of the location of the mechanical clearances between the mobile parts resulting from reversing the direction of the fluid in the valve body.
The appended drawings illustrate the invention.